Conventionally, an aqueous polymer compound/isocyanate based adhesive agent (EPI system) has been widely used for adhesive agents, paints (coating agents) and the like by taking advantage of its high water resistance. As a method for preparing it, the method of using as a base compound a water dispersible composition obtained by dissolving a polyvinyl alcohol powder in water with heating, adding an inorganic powder, an organic powder or an aqueous emulsion at predetermined ratios thereto and dispersing the mixture by mixing and stirring has been employed. Hereinafter, polyvinyl alcohol is simply abbreviated as PVA.
However, since the adhesive agent using the above water dispersible composition as the base compound is in a form of a water dispersion, there are problems of thickening, freezing and gelling in a land of severe cold during the winter and special measures such as temperature management are required for transport and storage. For disposal of reservoirs such as containers and metal drums for the aqueous compositions, the cost for collecting these cannot be ignored in a trend of making waste disposal suitable in the context of recent environmental concerns.
Therefore, an adhesive agent and a coating agent with high performance composed mainly of a powder composition have been requested in terms of easy transport and storage and having the capability of using containers such as paper bags and flexible container bags for easy disposal. Until now, as a powder type composition suitable for such a request, one powder type composition obtained by mixing inorganic powder or organic powder at a predetermined ratio with PVA powder, and one powder type composition obtained by mixing powder additives such as re-emulsified type powder emulsion have been proposed (Patent Document 1).
Patent Document 1: JP Hei-11-80484-A
However, when this powder type composition is re-dissolved (redispersed) in water at a site where it is used, it is forced to be dissolved (dispersed) incompletely due to crystallinity and insoluble (non-dispersible) piece formation of the PVA powder, and it has been pointed out that the insoluble (non-dispersible) pieces inhibit fluidity, adhesiveness and cohesiveness of the adhesive agents and coating agents.
On the other hand, a mixed powder composed of synthetic resin powder obtained by adding a PVA based polymer to an aqueous emulsion obtained from a dispersant and a dispersoid and drying the mixture and inorganic powder is known, and it has been described that the mixed powder is excellent in redispersibility, water resistance, film forming property when redispersed, and stability when left to stand at low temperature (Patent Document 2).
Patent Document 2: JP 2004-131719-A